Ferrous alloy



July 20, 1937. K. s. sl-:LJl-:sAE'rl-:R

FERROUS ALLOY Filed March 20, 1930 awa aan aan Patented July 20, 1937UNITED STATESPATENT OFFICE FERROUS ALLOY Kaare S. Seljesaeter, Chicago,Ill., assigner to.

Western Electric Company, Incorporated, New York, N. Y., a corporationof New York Application March 20, 1930, Serial No. 437,317

11 Claims. (Cl. 14S-21.5)

'I'his invention relates tov ferrous alloys and methods of producing thesame, and more particularly to alloys of iron with titanium, and tomethods of treating such alloys so as to produce certain desirablemechanical and magnetic characteristics.

An object of the invention is to provide an alloy in which certaindesirable physical and magnetic properties are4 produced by specialtreatment.

In accordance with the general featuresof the invention as embodied inone specific form thereof, a quantity of iron, preferably substantiallyfree of carbon, is alloyed with titanium and the mass is then cast inthe form of ingots, which are then formed by forging or other means intoany desired shape, or such shapes may if desired be formed directly fromthe molten metal. The forgings are then heated to a temperature justbelow the eutectic point of-the alloy, andthis temperature is maintainedfor a suftlciently long period of time to cause substantially all of theresulting solute constituentl to enter solution in the iron, and thealloy is then quenched at a sufficiently rapid rate to cause the soluteconstituent to remain in the iron in the form of a supersaturated solidsolution, after which the alloy is caused to assume a more stable stateby aging. The hardness of the alloy as quenched may be increased by morethan 200 percent by such aging, and the secondary hardness is retainedeven at elevated temperatures. In the manufacture of articles such asdies or permanent magnets from an alloy of the type just described, anarticle may be forged or otherwise formed from the alloy and the formedarticle then subjected to the above outlined heating, cooling, and agingoperations.

The above described and other objects and features of the invention willbe apparent from the following detailed description, taken in connectionwith the accompanying drawing, in-

f with its physical hardness.

Although it is not known with certainty what the solute constituent ofthe alloy is, it is believed that the titanium combines chemically witha part of the iron to form iron'titanid FesTi, which enters into solidsolution in the remainder of the 5 iron and may under certain conditionsbe precipitated in the form of microscopic or submicroscopic particlesdispersed throughout the alloy. The various steps constituting theprocesses described below are the same regardless of whether thetitanium is dissolved in the iron as titanium or as a compound, and itis to be understood, therefore, that in the following description andappended claims the term "solute constitucnt may include titanium eithercombined or uncombined as the case may actually be.

In practicing one method of producing alloys in accordance with theinvention,'a quantity 'of titanium greater than that which will entersolid solution in iron at room temperature, but not substantially morethan is soluble at the eutectic temperature, (3% -to 9% of titanium) isalloyed with iron and the resulting alloy'ls caused .to solidify. Thealloy is then heated at a temperatur of about 1200 to 1300 C. until asubstantially homogeneous solid solution is formed, and is then quenchedat a rate sufficiently rapid to cause most or all of the titanium to beretained in the iron in the form of a supersaturated solid solution, andthe alloy is subsequently aged at a temperature of about 600 C. orupwards.

The proper length of time and temperature of the solution forming step,quenching or supersaturating step, and the aging step, wherein the alloyis allowed to assume a more stable state, 5 together with the properproportions of iron and alloy ingredient, will vary with the propertiesdesired in the alloy and the uses to which the alloy is to be put.However, the following example has been found to produce a satisfactoryalloy for 40 permanent magnets. To 93 parts of substantially carbon-freeiron is added 7 parts of titanium, preferably in the form of aniron-titanium alloy rich in titanium, and the two ingredients areagitated in any known manner while in the molten state to produceahomogeneous alloy. The alloy is then cast into ingotsv and fabricatedinto desired shapes, which are then brought to a temperature just belowthe eutectic temperature, and maintained at such temperature for asufficient 5 time to produce a solid solution of the titanium in theiron. The parts are then quickly cooled by quenching, thus producing asolid solution of the solute constituent in the iron. The parts are thenheated to about '100 C., and maintained at 55 5 treatment, will be foundto have a magneticv remanence and coercive force higher than that ofiron-titanium alloys heretofore produced, and Ais suitable for use inpermanent magnets.

Referring to the drawing, curve B of Fig. 1 and curve E of Fig. 2indicate the magnetic remanence obtained by treating the alloy atvarious temperatures and subjecting the parts to a magnetizing force of1000 gilberts per centimeter, while the coercive force is indicated incurves C and F respectively. Both these characteristics reach a maximumwhen the alloy is aged at about 700 C. In order to obtain the maximummechanical hardness, the alloy may be aged at a temperature of about 600C'. as will be seen from an examination of curves A and D. An alloy agedat the latter temperature is suitable for use in dies for die castingmachines and for analogous uses since it is capable of withstanding hightemperatures without losing its hardness.

Alloys produced in accordance with the process lherein disclosed may beused for a variety of other purposes, and it is Within the scope of thisinvention to add to the alloy such other ingredients as may be founddesirable to adapt the alloy to the special purpose to which it is to beput. Thus,cobalt, tungsten, molybdenum, manganese, nickel. and vanadiummay be incorporated in the alloy in addition to the titanium to produceternary and quaternary alloys having such special properties as arenecessary to meet special requirements.

It is to be understood that the invention is not limited to theembodiments above described, but that it may be embodied in other forms,and is not to be limited except by the terms of the appended claims.

What is claimed is:

1. A magnet formed of an age-hardened sub- 45 stantially carbon-freeiron-titanium alloy containing substantially 5% of titanium.

2. The process of producing a magnet which comprises heating a binaryalloy containing substantially 5% of titanium and the balance iron 50 toan elevated temperature below its melting point, but suiciently high tocause the titanium to go into vsolution with the iron, quenching thealloy, reheating the alloy to a temperature below that of the initialheating, but sufficiently high and for a period of time sufcient toobtain a substantial increase in the magnetic hardness of the alloy, andmagnetizing the alloy to render it permanently magnetic.

3. A magnet formed of a precipitation-hard- 60 ened substantiallycarbon-free binary alloy of iron and titanium containing from about 3%to about 9% of titanium.

. 4. The process of making a magnet of a. binary alloy consisting offrom about 3% to about 9% 65 of titanium and the balance iron, whichcomprises heating the alloy to an elevated temperature below its meltingpoint but sufficiently high to cause the titanium to go into solidsolution with the iron, quenching the alloy, reheating the alloy atsubstantially the temperature below that of the initial heating at whichthe maximum magnetic hardness of the alloy is obtained for a period oftime suicient to produce a substantial improvement in the magnetichardness thereof, and magnetizing the alloy to render it permanentlymagnetic.

5. A magnet formed of a precipitation-hardened substantially carbon-freeiron-titanium a1- loy containing from vabout 3% to about 9% of titanium.

6. A magnet formed of a precipitation-hardened iron-titanium alloy whichmay contain minor amounts of other usual iron alloying ingredients, andfrom about 3% to about 9% titanium.

7. A magnet formed of a precipiation-hardened iron-titanium alloycontaining from about 3% to about 9% titanium and having a coerciveforce of over 30 gilberts per centimeter.

8. A magnet formed of a precipitation-hardened iron-titanium alloy whichmay contain minor amounts of other usual iron alloying ingredients andfrom about 3% to about 9% titanium, and having a coercive force of over30 gilberts per centimeter.

9. A method of making a magnet which comprises heating an iron-titaniumalloy containing from about 3% to about 9% of titanium to an elevatedtemperature below its melting pdint but suiiiciently high to cause theage-hardening element to go into solution with the iron, quenching thealloy, reheating the alloy to a temperature below that of the initialheating, but suiiiciently high and for a period of time suilicient toobtain a substantial increase in the magnetic hardness of the alloy, andmagnetizing the alloy to render it permanently magnetic.

10. A method of making a magnet which comprises heating an iron-titaniumalloy, containing from about 3% to about 9% of titanium and which maycontain minor amounts of other usual iron alloying ingredients, to anelevated temperature below its melting point, but sufriciently high tocause the age-hardening element to go into solution with the iron,quenching the alloy, reheating the allo-y to a temperature below thatlof the initial heating but suiiciently high and for a period of timesufficient to obtain a substantial increase in the magnetic hardness ofthe alloy, and magnetizing the alloy to render it permanently magnetic.

11. A method of making a magnet which comprises heating an iron-titaniumalloy containing from about 3% to about 9% of titanium to an elevatedtemperature below its melting point but sufficiently high to cause ahardening constitue'nt to go into solid solution with the iron,quenching the alloy, reheating the alloy at substantially thetemperature below that of the initial heating at which the optimummagnetic properties are obtained for a period of time sufficient toproduce a substantial improvement in the magnetic properties of thealloys, and magnetizing the alloy to render it permanently magnetic.

KAARE S. SELJESAETER.

